Preparation And Thermal Degradation Kinetic Of Modified Epoxy Resin As Crack Repairing Materials

Epoxy resin(EP),as a common thermosetting resin,is favored in the repair of concrete cracks due to its high crosslink density and chemical resistance.Polyurethane prepolymer(PUP)is an effective toughening agent for EP,which greatly improves the shortcomings of brittleness and toughness of EP repair materials.However,EP repair materials after PUP modification also have large viscosity in construction operation.The disadvantage of poor heat resistance.Therefore,based on the PUP modified EP,the raw material of the PUP raw materials,diphenylmethane diisocyanate(MDI)and polyether polyol(PPG),were used to modify the EP to reduce the viscosity of the repair material.The mechanical properties and infrared spectra of the modified EP repair materials were characterized.Finally,the thermal degradation kinetics of the modified EP repair materials was analyzed.In this paper,PPG,PUP and P-M modified EP repair materials were first prepared.The modifier content of the three modified EP repair materials was uniformly set to 0%,10%,20%,25%,30%.The effects of modification methods and modifier dosage on the performance of EP repair materials were investigated.Finally,using the Kissinger,FW-O and Friedman equations,the pyrolysis kinetics of different modified epoxy resins with different modification methods under 20% dosage and P-M modification were carried out.The results show that the addition of PPG and PM significantly reduces the viscosity of modified EP.When the PPG content is 20%,the viscosity reaches a minimum of 1021 mpa·s.When the dosage is 30%,the viscosity reaches a minimum of 1034 mpa.s;while the viscosity of PUP modified EP increased sharply with the increase of the dosage,when the PUP content was 30%,the viscosity reached a maximum of 43274mpa·s,and the initial setting time was only 5min.The three modification methods reduce the tensile strength of EP while reducing the tensile strength.The repairing performance of the cement concrete specimens before and after repairing with the repairing materials is used to indicate the repairing performance of the cracks.It is found that when the PM content is 25%,the flexural ratio is 1.96,which is greater than the unmodified EP of 1.51.The hydraulic concrete has a higher flexural strength.The results of scanning electron microscopy showed that P-M was added to transform the repair material from typical brittle fracture to ductile fracture.Ea data showed that no decrease in Ea value similar to PPG and PUP modification was observed in PM modified EP repair materials,and Ea value calculated at 20% dosage showed that E-(PM)-20% had the highest The thermal degradation activation energy,and the addition of PM has a certain improvement on the thermal stability of the modified EP.In the P-M modification,with the increase of P-M content,the thermal degradation Ea value of the repair material first increased and then decreased,and the repair material with higher dosage had lower thermal stability than the unmodified EP.P-M has a higher thermal degradation activation energy than unmodified EP at 20% and 25%.E-(P-M)-20% has the highest thermal degradation activation energy under five dosages.